1. Field of the Invention
The present invention relates to a disc drive device for recording and/or reproducing information to and/or from a disc-shaped recording medium, and more specifically, a magnetic head elevation control mechanism in a magneto-optical disc drive device.
2. Description of the Related Art
Conventionally, an information recording/reproduction device for recording and/or reproducing information using a recording medium, such as a magneto-optical disc, an optical disc, or the like, has been proposed. An example of recording media which have been proposed is a magneto-optical disc, or an optical disc accommodated in a cartridge. Conventional information recording/reproduction devices comprise an optical pickup and a magnetic head for writing and/or reading the information to and/or from the recording medium.
Such an information recording/reproduction device is widely used for an audio disc device, a video disc device, or an optical disc device which is used in a data storage device of a computer.
Among a number of optical disc devices, an MD (minidisc) device which uses a small-diameter disc for its media is widely used as a small audio disc device which is suitable for being easily carried by a user. Furthermore, as well as audio video (AV) equipment such as an MD device, personal computers have been rapidly becoming small and portable. Therefore, there is a demand for a much smaller and thinner optical disc device to be mounted to such equipment or a computer.
For use of a small-sized disc, an improvement in a recording density is essential in order to obtain a capacity sufficient for recording a large-data size image or a moving picture. In recent years, technologies for improving the recording density of the optical disc have advanced rapidly. Specifically, for a magneto-optical disc, various high-resolution reproduction schemes have been developed, and allow a high recording density which cannot be achieved by a conventional method.
In a drive device for a magneto-optical disc, a magnetic head which is used for recording the information is held at a tip of a leaf-spring-shape supporting member. The magnetic head is positioned so as to face a recording region of the disc via an opening which is provided in a cartridge. The magnetic head is coupled to an optical pickup by a coupling member. The optical pickup and the magnetic head are provided so as to interpose a disc therebetween. The magnetic head can be integrally movable with the optical pickup in a radial direction of the disc. For recording the information, the magnetic head is pressed toward the disc by the supporting member so as to be close to a disc surface or to be in contact with a disc surface. Thus, the magnetic head can apply a predetermined magnetic field to the disc from an opposite side to a spot of laser light directed by the optical pickup.
For reproducing the information, the magneto-optical disc drive device reads the information using the optical pickup, and therefore does not require the magnetic head. Usually, the optical disc drive device comprises a magnetic head elevation control mechanism. The magnetic head elevation control mechanism moves the magnetic head close to the disc for recording information, and for separating and retracting the magnetic head from the disc surface for reproducing information to prevent abrasion or damage of the disc surface or the magnetic head.
Hereinafter, such a conventional magneto-optical disc drive device will be described with reference to the drawings.
FIG. 9 is a perspective view illustrating a cartridge to be used in a conventional disc drive device.
In FIG. 9, a cartridge 31 stores a disc 32 in a manner which enables the disc to rotate relative to the cartridge 31. Also, the cartridge 31 has an opening 33 which allows an optical pickup and a magnetic head to face a recording surface of the disc 32. When the cartridge 31 is mounted to the disc drive device, a shutter 34 is moved so as to expose the opening 33. When the cartridge 31 is removed from the disc drive device, the shutter 34 moves back to its original position so as to cover the opening 33.
FIG. 10 is a plan view illustrating a structure of a conventional disc drive device 50. FIG. 11 is a cross-sectional view illustrating the conventional disc drive device 50 taken along line A—A of FIG. 10.
For further understanding, FIGS. 14A through 14C each show a schematical cross-sectional view of the conventional disc drive device 50. Now, with reference to FIGS. 14A through 14C, an operation of the conventional disc drive device 50 to contact/separate the magnetic head with/from the disc will be described.
FIG. 14A shows the conventional disc drive device 50 without the disc cartridge 31 being inserted therein. In FIG. 14B, a magnetic head 40 contacts the disc 32. In FIG. 14C, the magnetic head 40 is apart from the disc 32. When the disc cartridge 31 is inserted into the disc drive device 50, each component of the disc drive device 50 is positioned as illustrated in FIG. 14B, allowing recording of information to the disc. Specifically, the magnetic head 40 which is attached to a tip of a suspension 41 contact the disc 32, while a lifting plate 46 is out of contact with the suspension 41. For reproducing information, the magnetic head 40 is not required, and therefore the lifting plate 46 pivots to lift the suspension 41. As a result, as shown in FIG. 14C, the magnetic head 40 is apart from the disc 32.
As shown in FIG. 14B, the conventional disc drive device 50 requires an entire height of h1 for allowing the lifting plate 46 to pivot. Therefore, the thickness of the device 50 increases.
Next, with reference to FIGS. 10 through 13, the conventional disc drive device 50 will be described in more detail.
As shown in FIGS. 10 and 11, the cartridge 31 storing the disc 32 is held by a holder 39 in a position in which information can be recorded/reproduced. The holder 39 is attached to a chassis 35 by pivot axes 60 to be pivotably elevated. The pivot axes 60 are provided at two corners of the chassis 35 opposite to an insertion side for a cartridge. In the chassis 35, a guide shaft 38 is provided. Along the guide shaft 38, an optical pickup 37 is movable by a driving motor (not shown) in a radial direction of the disc 32. The optical pickup 37 faces the disc 32 via the opening 33 on a bottom surface of the cartridge 31. Further, a spindle (not shown) is provided in a center of the chassis 35, and rotates the disc 32 accommodated in the cartridge 31.
A magnetic head 40 is attached to a tip of a suspension 41, and coupled to the optical pickup 37 by an angled member 43. The magnetic head 40, the suspension 41, the optical pickup 37, and the angled member 43 are integrally movable in the radial direction of the disc 32. A magnetic head base 42 is held on an upper portion of the angled member 43 in parallel to a recording surface of the disc 32, and is pressed in the direction of the disc 32 by a leaf-spring 57.
In this state, the suspension 41 bends upward from its natural state, and locates the magnetic head 40 so as to contact and press the disc 32. Thus, the magnetic head 40 glides on the disc 32 with a predetermined downward thrust (i.e., toward the disc surface). A magnetic field is applied to the disc from an opposite side to a spot of laser light directed by the optical pickup 37 to record the information.
A positional variation of the magnetic head 40 and variation in angles between the magnetic head 40 and the recording surface of the disc 32 caused by wobbling of the disc 32 is absorbed by the deformation of a gimbal suspension 53 at the tip of the suspension 41. The thrust of the magnetic head 40 which presses the disc 32 is set to be small in order to avoid excessive bending of the disc 32. Accordingly, the gimbal suspension 53 has very low rigidity, and is flexible.
The suspension 41 must be configured such that the magnetic head 40 contacts the disc 32 via the opening 33 of the cartridge 31. The suspension 41 is bent to avoid contact with objects provided between an attached portion of the suspension 41 to the angled member 43 and the recording surface of the disc 32.
Under the cartridge 31, a drive mechanism (not shown) is provided. An engaging portion 45 extends from a side surface of the holder 39 to a bottom surface of the cartridge 31. The sliding plate 44 is driven so as to slide in a direction of cartridge insertion.
Furthermore, a lifting plate 46 is pivotably provided on the upper surface of the holder 39. When the sliding plate 44 slides in a direction represented by arrow b (direction b) toward the pivot axes 60, an inclined protrusion 48 of the sliding plate 44 lifts up a protrusion 47 of the lifting plate 46. Thus, the lifting plate 46 inclines such that an edge 46a thereof is lifted. By the inclination of the lifting plate 46, the magnetic head suspension 41 which is positioned above the lifting plate 46 is lifted up irrespective of the position where the magnetic head suspension 41 locates the magnetic head 40 from the inner to the outer periphery of the disc 32. Therefore, the magnetic head 40 is brought into a state in which the magnetic head 40 is apart from the disc 32 (hereinafter, referred to as a lifted-up state).
Usually, in a disc drive device, a magnetic head contacts a disc only during recording, and the magnetic head is lifted up during reproduction in order to prevent abrasion or damage of the disc surface or the magnetic head.
FIG. 12 is a plan view illustrating the conventional disc drive device 50 with the magnetic head in the lifted-up state. FIG. 13 is a cross-sectional view illustrating the conventional disc drive device 50 with the magnetic head in the lifted-up state taken along line A—A of FIG. 12.
In FIGS. 12 and 13, the sliding plate 44 is slid in the direction b toward the pivot axes 60 by a drive mechanism provided under the holder 39. The inclined protrusion 48 of the sliding plate 44 goes under the protrusion 47 of the lifting plate 46, and thus the lifting plate 46 is pivotably elevated. Therefore, the magnetic head suspension 41 is deformed upward and lifted. At the same time, the tip of the magnetic head suspension 41 contacts the bottom surface of the magnetic head base 42. The gimbal suspension 53 of the magnetic head suspension 41 is deformed downward. The magnetic head 40 and the magnetic head suspension 41 are accommodated between the upper surface of the cartridge 31 and the magnetic head base 42.
The tip of the magnetic head suspension 41 is made to contact the magnetic head base 42 for the following reasons. One reason is to prevent an entire thickness of the device 50 from being increased because the tip of the magnetic head suspension 41 protrudes above the height of the magnetic head base 42. Another reason is to prevent the magnetic head suspension 41 from being deformed due to shock or an external force which the magnetic head may experience if dropped when in the lifted-up state.
The above conventional disc drive device 50 and the like has the following problems.
As shown in FIG. 13, a thickness of the device 50 (which is indicated by “D”) is determined by the sum of the thicknesses of the chassis 35, the cartridge 31, and the magnetic head elevation control mechanism which is located above the cartridge 31. To lift the magnetic head 40 so as to contact the magnetic head base 42 which is located above the cartridge 31, a lift amount L of the lifting plate 46 must be at least a distance H shown in FIG. 13 between the upper surface of the cartridge and the disc surface. If the lift amount L is smaller than this required amount, the magnetic head 40 cannot be sufficiently brought apart from the disc 32, and the magnetic head 40 may collide with the disc 32 during reproduction due to vibration or applied shock. Further, if the magnetic head 40 cannot contact the magnetic head base 42, the gimbal suspension 53 may be deformed due to shock caused by dropping, or the like. Therefore, the lift amount L should be sufficiently large, and thus the entire thickness of the device 50 cannot be made thin.
As described above, when the drive mechanism for controlling an elevation operation of the magnetic head 40 is provided above the cartridge 31, the thickness of the device 50 significantly increases. Even if the drive mechanism is provided under the cartridge 31, the thickness of the device 50 may be increased by the thickness of the drive mechanism. Therefore, even though the spindle and optical pickup are thin, it is difficult to make the entire thickness of the device 50 thin. Moreover, in this case, driving force must be transported from the drive mechanism under the cartridge 31 to the lifting plate 46 which is located above the cartridge 31. Therefore, the structure of the device 50 is complicated.